/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package javax.servlet.jsp;

import javax.servlet.Servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * <p>
 * The JspFactory is an abstract class that defines a number of factory
 * methods available to a JSP page at runtime for the purposes of creating
 * instances of various interfaces and classes used to support the JSP
 * implementation.
 * <p>
 * A conformant JSP Engine implementation will, during it's initialization
 * instantiate an implementation dependent subclass of this class, and make
 * it globally available for use by JSP implementation classes by registering
 * the instance created with this class via the
 * static <code> setDefaultFactory() </code> method.
 * <p>
 * The PageContext and the JspEngineInfo classes are the only
 * implementation-dependent classes that can be created from the factory.
 * <p>
 * JspFactory objects should not be used by JSP page authors.
 */

public abstract class JspFactory {

	private static volatile JspFactory deflt = null;

	/**
	 * Sole constructor. (For invocation by subclass constructors,
	 * typically implicit.)
	 */
	public JspFactory() {
		// NOOP by default
	}

	/**
	 * Returns the default factory for this implementation.
	 *
	 * @return the default factory for this implementation
	 */

	public static JspFactory getDefaultFactory() {
		return deflt;
	}

	/**
	 * <p>
	 * set the default factory for this implementation. It is illegal for
	 * any principal other than the JSP Engine runtime to call this method.
	 * </p>
	 *
	 * @param deflt The default factory implementation
	 */

	public static void setDefaultFactory(JspFactory deflt) {
		JspFactory.deflt = deflt;
	}

	/**
	 * <p>
	 * obtains an instance of an implementation dependent
	 * javax.servlet.jsp.PageContext abstract class for the calling Servlet
	 * and currently pending request and response.
	 * </p>
	 * <p>
	 * <p>
	 * This method is typically called early in the processing of the
	 * _jspService() method of a JSP implementation class in order to
	 * obtain a PageContext object for the request being processed.
	 * </p>
	 * <p>
	 * Invoking this method shall result in the PageContext.initialize()
	 * method being invoked. The PageContext returned is properly initialized.
	 * </p>
	 * <p>
	 * All PageContext objects obtained via this method shall be released
	 * by invoking releasePageContext().
	 * </p>
	 *
	 * @param servlet      the requesting servlet
	 * @param request      the current request pending on the servlet
	 * @param response     the current response pending on the servlet
	 * @param errorPageURL the URL of the error page for the requesting JSP, or
	 *                     null
	 * @param needsSession true if the JSP participates in a session
	 * @param buffer       size of buffer in bytes, {@link JspWriter#NO_BUFFER}
	 *                     if no buffer, {@link JspWriter#DEFAULT_BUFFER}
	 *                     if implementation default.
	 * @param autoflush    should the buffer autoflush to the output stream on
	 *                     buffer overflow, or throw an IOException?
	 * @return the page context
	 * @see javax.servlet.jsp.PageContext
	 */

	public abstract PageContext getPageContext(Servlet servlet,
	                                           ServletRequest request, ServletResponse response,
	                                           String errorPageURL, boolean needsSession, int buffer,
	                                           boolean autoflush);

	/**
	 * <p>
	 * called to release a previously allocated PageContext object.
	 * Results in PageContext.release() being invoked.
	 * This method should be invoked prior to returning from the _jspService()
	 * method of a JSP implementation class.
	 * </p>
	 *
	 * @param pc A PageContext previously obtained by getPageContext()
	 */
	public abstract void releasePageContext(PageContext pc);

	/**
	 * <p>
	 * called to get implementation-specific information on the current JSP
	 * engine.
	 * </p>
	 *
	 * @return a JspEngineInfo object describing the current JSP engine
	 */

	public abstract JspEngineInfo getEngineInfo();

	/**
	 * <p>
	 * Obtain the <code>JspApplicationContext</code> instance that was
	 * associated within the passed <code>ServletContext</code> for this web
	 * application.
	 * </p>
	 *
	 * @param context the current web application's <code>ServletContext</code>
	 * @return <code>JspApplicationContext</code> instance
	 * @since 2.1
	 */
	public abstract JspApplicationContext getJspApplicationContext(
			ServletContext context);
}
